Functionalized silicon surfaces for biological and chemical sensors

Carboxyl-terminated monolayers are usually a convenient starting point for the elaboration of chemical or biological sensors as they can be easily "activated" through a two-step amidation reaction for covalently grafting probes at the surface. In this work we study surface activation (-COOH + NHS/EDC → -COOSuc) on flat silicon surfaces and show that the operating conditions are critical to maximize the density of -COOSuc sites, to reduce the density of remaining COOH sites and, last but not least, to avoid by product formation and/or adsorption. As a proof of concept we apply this specific chemistry and present the design of an efficient and reusable Si-based biological microarray, which, in addition allows for in situ monitoring of the fluorescence intensity. Preliminary results also demonstrate the electrochemical detection of metallic cations by surface complexation with oligopeptides immobilized on porous silicon.